My Sleeping, Howling Dog

Question
I have had a mixed terrier for over 8 years - I found him abandoned.  He has been a very good dog and I have had no problems.  Recently, he has started howling and whining, mostly during the night when he is sleeping.  When I soothe him and tell him it's okay, he stops, but sometimes will begin again.  He also did this on the way home from vacation in the car (he travels very well) - he has never done this before.  When in the car, he started howling and whining; I put him in my lap, soothed him, and he went back to sleep - only to wake again in a few minutes, howling and whining.  This is very scary to me.  (He continues to eat fine, exercise, and is otherwise normal.  He is diabetic, but has been for over 6 months and is doing fine.  The whining started about a month ago and has escalated.)

Thank you for whatever advice you can give me.

Answer
Jan, I would be concerned that he may have something health-related going on, such as a tumor, or maybe painful joints. If it were me, I'd take him to the vet to make sure that isn't the case before I did anything else.

Do you know how old he is? He could be developing dementia, or perhaps he is just 'talking' in his sleep. I would recommend that you stop giving him attention when he does it, because he could figure out that doing it is a good way to get what he wants. What if you ignore him completely when he does it?